Spark plug



T. T. BATHURST SPARK PLUG.

APPLICATION man NOV. 12, 192]- 1,430,429. fi pt 25%, 1922.

v "f $3M,

A TTORNEY Patented Sept. 2 6, 19 22.

UNITEDSTATES- PATENT OFFICE.

TI-IdMAS T. BATHURST, OF KANSAS CITY, MISSOURI.

SPARK PLUG.

Application filed November 12, 1921. Serial 180. 514,433.

4 To call whom it cnay concern." 1

Be it known that I, THOMAS T. ,BATHU'RST,

'a citizen of the United States, residing at Kansas City, in the county of Jackson and State of Missouri, have invented certain new and useful Improvements in Spark Plugs;

' and I do declare the following to be a full,

clear, and exact description'of the invention,

such as will enable others skilled in the art to which it appertains to make and use the same, reference beiiig had to the accompanying drawings, and to the figures of reference marked thereon, which form a part of this specification.

This invention relates to spark plugs and the primary object thereof is to provide a rugged, durable, inexpensive and'efiie-ient plug, the construction being such that provision is made for renewals in a most convenient manner. p 4

The invention contemplates the prov sion of means whereby the porcelain w lich cartested for rice the positive electrode may be confined Wltl'llll a casing consisting of a plug or skirt member to be screwed into the engine cyl: inder wall and a separate cap member. The

skirt member may be installed as a permanent part of'the engine cylinder with the cap member removable therefrom so that the porcelain may be removed for inspection, repairs orrenewals.

The cap member is adjustable, with respect to the skirt member in which the porcelain is seated so that the porcelain may unseat during the compression stroke of the engine to permit the fuel charge to be forced past the electrodes to free them as well as the lower portion ofthe porcelain of carbon deposits'or other e'xtraneousmatorifice surrounded by the wall of the skirt member and prevent the admission of atmosphere through the spark plug into the engine.- Therefore, it will be apparent that the porcelain may function as a check valve during the operation of cleaning the electrodes or during the time that the engine is being compression or' to determine whether or not the spark plug electrodes are properly functioning.

The portion ofthe porcelain which is seated within the skirt member or'portion is provided with a covered shoulder curved on a diiferent arc than the curvature of the seat scrthat there will be a line contact between.

ter. Upon the suction stroke of the piston the porcelain will seat so asto valve off the the porcelain and its seat. This is an advantage over a flat contact because liability of leakage due to interposition of carbon or gritty matter will be eliminated.

Means-is also provided for eliminating liability of cracked porcelains due to variations in the coefficients of expansion between the spark plug shell'or casing and the porcelain and to this end I arrange about the porcelain a, shell having certain yielding portions which contact with the skirt member and the cap member so, that the porcelain may expand without contacting directly with either the skirt member orthe cap member.. The'tendency to expand, however, is reduced by reason of the fact that a cooling space is provided about the porcelain so as to maintain the temperature of the porcelain relatively low.

Another advantage in the construction of the device is that the engine can be primed through the spark plug by introducing fuel liquid 'intothc cylinder thcrethrough and I tion and partly in section through the rcmovcd porcelain.

Fig. 4 is 'a vertical, kingitudinal, sectional view through the spark plug showing the porcelain unscatcd to permit the exhaustion of the contents of the combustion cylinder therethrough or to permit priming into the cylinder.

Fig. 5 is a similar view of the porcelain seated so as to valve the skirt member of the casing or shelf, and

Fig. 6 is a detail perspective view of the parts disassociated, showing the introd'uction of the'porcelain as a renewal or during the assembly.

The spark plug shell or casing is shown as Ill) . Fig. 3 ls an enlarged view partly in clcvaconsisting of two members 1 and 2. I designate the member 1 the skirt member because it consists of a cylindrical body havpose of which will be described hereina er.

The skirt member is separated from the 'collar 5 by a polygonal collar 10, by means of which a wrench may be used to introduce thethreaded skirt portion into-the threaded portion 11 of the engine cylinder 12. (see Fig. 6)

The skirt member is provided at its 'up-" per end with a porcelain-receivin seat 13,

upon which the enlargement or'co lar 14 of the porcelain 15 may rest. The edge 16 of the collar let is curved on an are generated;

from a shorter radius than that of the seat 13 so that there will be a line contact of the porcelain on the seat, the porcelain being held thereon by the cap member 2,which has a lower internally threaded portion 17 to engage the threaded collar 5, as clearly seen in F ig. 2.

' The'upper end of the collar 14 is engaged by a seat or flange 18, which rests thereupon and cooperates with the seat 13 to clamp/ .the porcelain rigidly within the shell, the

side wall'of the; cap 2 having a plurality of perforations 19 to permit air to circulate about the collar let to permit priming through theorifice 3 and to permit the exhaust from'the cylinder to pass to atmosphere when the collar is unseated.

By reference to Fig. 3"it will be observed that the collar 14 of the porcelain 15 is a metallic shell of greater length than the porcelain portion 14 and that the shell isspun over the upper and lower portions of the porcelain portion 14 so as to," provide resilicut or yielding ends 20 and 2l between which and the upper and lower ed es of the portion 14' are yielding gaskets )2 and 23.

It will also be observed that the shell is slightly larger in diameter than-the part 14 so if the portion 14' expands, it may expand within the space between the wall of the col- 19.1 14 and the porcelain portion 14, thereby preventing liability of crushing effect of the -rigid shell against the portion during its exansion. If the porcelain grows or expands ongitudinally, its expansion can be provided for by the gashe'ts 22 and 23 as well as by the yielding flanges 20 and 21. Therefore it will be apparent that there can be considerable expa'nsion and contraction of the orc'elain 15 without liability of the pores ain cracking, which is a serious defect in most plugs now on the market.

Attention is also directed to the fact that the porcelain carries the usual positive electrode 24, extending below" the lower end thereof and terminating at its upper end in a binding post 25, in the usual manner.

In actual practice I prefer to have the diameter of the bore 26 of the cap 2 slightly in excess of the shell or collar 14 so that when to seat each time it is moved ontothe seat 13. Therefore, liability of the plug leaking after extended use will be reduced to a minimum.

gine cylinder as a permanent part thereof, it. will be apparent that an extremely efficient;

means is provided for renewals- For exampl, the porcelain'can be constructed as .shownin Fig. 3 as a unitary structure so that in the event that it becomes necessary to take out the porcelain for inspection, repairs or, more important, for renewals, it will be only necessary to unscrew the cap member 2, remove the porcelain and, if a renewal is required, introduce a new porcelain, screw back the cap, and the plug is complete. I h I The efiiciency in makingthe renewal is. due to a large extent to the fact that the line contact 1s provided so that the pores lains are interchangeable in any of the skirt portions and do nothav'e to be setespecially .for any particular plug casing and because there is a line contact, the fact that a pores lain has been in the plug for some time will not prevent the renewal from perfectly fitting the first time it is introduced into the old shell.

By providing the parallehoppositely rected fingers 8 and 9, which cimstitute the negative electrode, it will be apparent that be possible to make them properly function because there will always be a portion of a negative electrode sufiiciently close to the end 28 to permit the proper functioning of the Vghen the parts are assembled and it is desired to clean the plug, it will be only necessary to slightly back screw the cap 2. There- Sincejthe spark plug shell or casing confore, the incoming raw charge of fuel introduced into the combustion cylinder may be forced over the electrodes and lower portion of the porcelain and out through the ports or holes 19. On the suction stroke of the piston, however, the porcelain will re-seat itself, as shown in Fig. 5, so that atmosphere will not 'be drawn through the plug, the

' cleaning charge in each instance being the p and into the combustion chamber of the cylinder."

Whenever it is desired to renew or mspect the porcelain, this can be accom-.

plished by removing the parts, as shown in Fig. 6, it being readily apparent that the renewal" feature is a very important part of the invention.

' Aside from the other advantages, the porcelain is so constructed that liability "of cracking due to expansion will be practically eliminated.

Attention is also directed to the fact that since the bore 26 is slightly larger in diameter than the collar 14 so as to provide a space, air is permitted to circulate through the ports 19' and between the collar and the surrounding wall of the cap 2 so as to maintain the temperature of the porcelain at its thickest portion relatively low and since the collar 14 is spun over: the portion 14: with the lower flange 21 resiliently disposed with respect to the end portion 14', it will be apparent that when the porcelain functions as a check valve to seat and unseat when the parts are in the position shown in Figs. 4 and 5, the blow or impact of the porcelain against the seat 13 will not re suit in breaking or chipping of the porcelain which might be true if the porcelain cai ue indirect contact with its seat. There fore, the reciprocatory action of the porceiain will not result in any ill efi'ect on the porcelain.

it should be remembered that when the porcelain is moved off its seat, the compression in the combustion chamber is destroyed. The spark will. still. bridge the gap between the end 28.01? the electrode 24 ,,and the electrodes 7 and 8 but no explosion can take place because the fuel charge will not be under compression. Therefore, the lower intake charge will be forced over the electrodes 7 and 8 and around the porcelain to act as a cleansing fluid to remove accuundated carbon, the raw fuel charge being more eiiicacious than the exploded charge; hence, I can provide means for distributing or contacting the raw fuel charge over the parts to be cleaned without any special attention other than to back screw the cap 2 to permit the porcelain to move off its seat and destroy the compression, which is essential to combustion in an engine of the type to which the plug is to be attached.

' Therefore, it will be seenthat the device isv inexpensive, rugged, eflicient and that it eliminates practically all of the causes of trouble heretofore encountered in various types of spark plugs.

What I claim and desire to ters Patent is:

l. A spark plug comprising a skirt member and a cap member, the skirt member" having a seat, a porcelain having a shoulder to rest 'upon the seat, the a'rcof the shoulder being less than the arc of the seat whereby secureby- Leta line of contact is provided between-the porcelain and the seat and means for ad justably securing the cap to the skirt member, the cap member being adapted to normally hold the porcelain rigid with respect I to the skirt member and adapted to be adjusted on the skirt member to allow the porcelain to reciprocate from and toward its seat.

2. A porcelain -for spark plugs comprising a porcelain body having a central electrode extending therethrough, one end of other a contact point, the porcelain having an intermediate rigid collar providing upper and lower shoulders, a resilient shellv surrounding the collar having flanges projecting over the upper and lower shoulders and cushions between the flanges and the shoulders to provide resilient bearing surfaces.

3. A spark plug'comprising a skirt memwhich. constitutes a binding post and the beer and a cap member, the skirt member having a tapered seat at,its upper end, the cap member having va central opening at its upper end surroundd by a flange constituting a seat, a porcelain having a collar interposed between th'e two seats and adapted when the cap is in the one position to reciprocate between the two seats, said collar forming a shoulder, the arc of'the' shoulder and the are of the seat being such that a narrow line of contact is established, yieldingcontacts on the porcelain for engagement with the respective seats, the flanged opening of said cap loosely engaging said porcelain to cause the same to properly seat itself on sai'cltaperecl'seat.

4. A spark plug comprising a skirt memher and a cap member, the skirt member having a tapered seat at its upper end, the cap member having a central opening at its upper end surrounded by a flange constituting a seat, 'a porcelain having a collar interposed between the two seats, and a metallic casing; about the collar 7 but spaced from the periphery thereof, the ends the casing being turned-overat the ends of the collar, resilient seats between the ends of the collar and the ends of the casing t he are of the ends of the casing of said tapered seat being such that a narrow line 01 0011- ture.

THOMAS T. BATHURST. 

